Research in my laboratory investigates the brain processes underlying the effects of drugs and stress hormones on memory storage. I began my studies of neurochemical influences on memory storage when I was a graduate student. In early research I found that, in rats, stimulant drugs enhanced memory when they were administered immediately after training. These findings suggested that the drugs acted to stimulate memory consolidation. Subsequent findings from my laboratory that posttraining administration of stress hormones released by training experiences enhance memory consolidation indicate that activation of endogenous hormone systems plays an important role in modulating the storage of recently acquired information.

Considerable evidence from my laboratory indicates that the basolateral region of the amygdaloid complex (BLA) is critically involved in mediating drug and hormone effects on consolidation. Lesions and temporary inactivation of the BLA block the drug and hormone effects on memory. Furthermore, infusions of drugs and hormones administered directly into the BLA have effects on memory that are comparable to those of systemic injections. Our findings indicating that beta-adrenergic antagonists infused into the BLA block the effects of many drugs and hormones on memory suggest that the effects involve influences on the release of norepinephrine (NE) and activation of beta-adrenoceptors in the amygdala. In support of this view we have found, in experiments using in vivo microdialysis, that stimulation of the kind typically used in training rats induces the release of NE in the amygdala, and that drugs and hormones affecting memory modulate NE release in the amygdala. Additionally, the amount of NE released following training correlates highly with subsequent retention.

Findings of other recent experiments indicate that the amygdala influences memory by modulating the functioning of other brain regions involved in information storage. Current studies in my laboratory focus on the interaction of the amygdala with other brain regions in regulating memory storage.

Berlau, D.J. and McGaugh, J.L. Enhancement of extinction memory consolidation: The role of the noradrenergic and GABAergic systems within the basolateral amygdala. Neurobiology of Learning and Memory, 2006.